How to add a class for NotesHttpRequest in a notes agent?

I would like to make a simple Notes HTTP Request over a Notes agent, but there is always the following message:

Class or type name not found: NOTESHTTPREQUEST

My Code:

Dim webRequest as NotesHTTPRequest
Set webRequest = NotesSession.CreateHTTPRequest()
Call webRequest.get(URL$)

Question:

What do I have to do, to import the required class for a simple GET Request over Lotus Script in a notes agent?

NotesHTTPRequest is new with Notes/Domino 10.x. So you need to use Notes/Domino 10.x to use it.